Traditional roof technologies construct elevated covers to buildings. A roof typically comprises a layer of impermeable tar, tarpaper or concrete laid over a wood or metal platform (deck) of corrugated metal sheeting. While a roof seals a building from the environment, it also results in substantially reduced daylight illumination, the loss of a heat source in cool seasons and the collection of heat in warm seasons. Skylights may or not be fitted to improve illumination but may add to the heat gain in the warmer months. Similarly, wall construction is primarily a means of sealing out the elements from the inside of a structure.
Solar energy is tantalizing in both its promise and its evasiveness. The ultimate objective is to utilize solar energy to heat, cool, provide electricity, and light structures efficiently and to reduce the need for energy from other sources. Various approaches have been suggested for achieving each of elements of this objective.
In a “German Roof” a series of windows are present on the roof of a building. In cross section these appear as a saw tooth pattern on the roof. They provide both light and heat (but usually only when they face the sun).
Referring to FIG. 1, the “Minnesota window heater” is illustrated. This unit is placed in a window 27. The suns rays are absorbed on a black (or dark)) panel 25 heating the air in the vicinity of the panel. The air rises through the heater (as noted by the arrows, causing more cool air to be drawn into the heater through opening 24. Heated air is expelled through opening 26 into the room.
Technologies that collect some aspect of solar energy introduce some negative side effects that require energy consumption to offset. Solar heat exchangers for water and space heating or for electrical energy collection cause a build up of heat in summer months. This heat needs to be actively dissipated or mechanically cooled at an expense. Similarly, solar technologies that are designed to heat water and convert solar energy to electrical energy ignore winter heating needs. Skylights and solar daylighters provide illumination but just as often add heat (via direct sunlight) as fast as illumination and increase the “solar oven” effect of most buildings.
At additional expense and effort, solar photovoltaic panels may be laid horizontally or framed to sit at an angle. For example, photovoltaic (amorphous) on plastic substrate is available to lay in pans of standing seam metallic roofing. While photovoltaic panels permit the production of electricity, the per-kilowatt cost of generation is high. Additionally, the panels block solar illumination of the structure thereby trading off one form of solar energy for another.
“The SOLARWALL® Solar Heating System” made by Conserval Engineering (Conserval Engineering) heats air in the winter. A southern wall is metal clad (aluminum or steel) on its exterior. A cavity is formed between the building's southern wall and the metal cladding. A ventilation fan, positioned at the top of the cavity creates reduced pressure within the cavity. Outside air is drawn in through holes in the metal cladding due to air pressure differential. The dark colored cladding is heated by solar radiation. The external air that is drawn over the metal cladding is heated and captured by openings in the metal cladding and collected in the wall cavity. The warmed air from the wall cavity rises to a plenum at the top of the cavity and is ducted to a circulation fan. The warmed air is circulated throughout the building. Applications include using the metal cladding as roofing material and overlaying the metal cladding with photovoltaic panels to produce electricity.
The Conserval Engineering approach, described above, is also described in U.S. Pat. No. 4,899,728 to Peter et. al, entiled “Method and Apparatus for Preheating Ventilation Air for a Building”, ('728) and U.S. Pat. No. 4,934,338 to Hollick et. al, entitle, “Method and Apparatus for Preheating Ventilation Air for a Building”, ('338). The description for patents '338 and '728 are virtually the same (the '338 patent is a divisional of the '728 patent). Effectively, both citations are for an exterior wall passive solar heat collector for heating outside air.
In Canadian Patent 1,196,825 issued to Hollick and entitled “Method for Preheating Ventilation Air in a Building” ('825), describes an outer transparent glazing to a south wall that allows solar energy to penetrate the glazing material (glass, plastic or the like) and be absorbed on a black painted building wall. There is a space between the glazing material and the building wall forming an air chamber. Outside air is drawn into the air chamber through an opening at the bottom of the glazed material. The air is heated by the building wall which has become heated from absorbing solar energy. The air rises and is distributed by fan and duct work through the building for heating purposes. If heating is not desired, the hot air is allowed to vent to the outside.
In U.S. Pat. No. 4,449,347 issued to Rooney and entitled “Solar Collection Building Truss,” ('347) describes a solar collector integrated into a building truss that can be fabricated at a building site or pre-fabricated at a factory. The '347 patent teaches use of reflective surfaces to direct light to a heat absorbing member connected to a heat exchanger or other means for storing heat generated by the heat absorbing member. A similar truss was described in U.S. Pat. No. 4,237,869 also issued to Rooney, entitled “Solar Collector.”
U.S. Pat. No. 6,201,179 issued to Dalacu and entitled “Array Of Photovoltaic Modules For A Integrated Solar Power Collection System,” describes a solar powered collection system comprising a variety of arrays for generating electricity.
U.S. Pat. No. 4,674,244 issued to Francovitch and entitled “Roof Construction Having Insulation Structure Membrane And Photovoltaic Cells,” teaches a means for roof construction that integrates photovoltaic cells into the roof structure.
U.S. Pat. No. 5,092,939 issued to Nath et. al., and entitled “Photovoltaic Roof Method Of Making Same,” describes a roof structure comprising panels in which a photovoltaic layers has been incorporated.
U.S. Pat. No. 5,452,710 issued to Palmer and entitled “Self Sufficient Apparatus And Method For Conveying Solar Heat Energy From An Attic,” ('710) describes a solar energy absorbing roof that heats air in the attic below the roof. In '710, solar-generated heat is collected from the attic stored and/or distributed within the building. Fans and other electrical apparatus needed to capture, distribute, and store the collected heat are powered by photovoltaic cells placed on the roof.
U.S. Pat. No. 4,466,424 issued to Lockwood and entitled “Solar Collector System For Standing Seam Roofs,” ('424) describes a solar collector system incorporated into a standing seam roof. The collector is formed by securing two transparent sheets to the standing seams of a roof panel to form two channels, one acting as a heat exchanger and the other an insulating chamber. Sun light impinges on the bottom of the roof panel and heats it. Air travels over the heated surface of the bottom of the roof panel and is heated and collected by ductwork located near the center ridge of the roof.
U.S. Pat. No. 4,103,825 issued to Zornig and entitled “Solar Heated And Cooled Dwelling,” describes means for collecting heated attic air during the heating season and removing unwanted heated attic air during the cooling season.
U.S. Pat. No. 4,201,188 issued to Cummings and entitled “Solar Collector And Heat Trap,” describes a solar collector and heat trap for the collection of heat in an attic area of the home for subsequent distribution throughout the home.
Finally, French Patent 2,621,943 was issued to Hernecq for a heat collection system in the attic of a home for distribution throughout the home.
While these inventions are useful for producing heat or photovoltaic energy, they do not represent an integral construction member that has the capability of not only collecting heat for use in heating inside air but also producing electrical energy from the heat air collected.
What would be useful is a means of integrated solar collection into construction that would make efficient use of sunlight for illumination and solar energy for generation of heat and electricity without unwanted structural heating, and that would intercept sunlight generated heat for capture and use during winter and diversion away during summer. It would also be useful if sunlight and solar generated heat could be used to generate electricity and hot water under all seasonal conditions during daytime periods of peak electrical power consumption.